Alwyn Young (LSE) was here on Monday, speaking in the CREI Macro seminar. He gave his talk about the positive side of AIDS - how a reduction in fertility, induced by the spread of AIDS in Africa, creates the resources with which to soften the blow of the disease. Together with his earlier article ""Gift of the Dying"", I think this is some of the boldest thinking in development economics. This time, I wasn't so convinced. Young shows how fertility declines rapidly in countries that are suffering particularly badly from the epidemic, but the causal channels remain slightly vague. I am not sure that country-specific trends are a good way to get rid of omitted variables. Of course, from a policy perspective, you don't really have to think that this is causal - that the AIDS epidemic really causes people to reduce their fertility. As long as the two trends coincide, for whatever reason, the countries in question have additional resources that can be used to alleviate suffering and to combat the disease.